It is said that whether in terms of distance covered, number of endpoints generated or value invested, the most predominant transmission medium for communications networks worldwide is that of copper. This has resulted from the use of copper as a transmission medium in the earliest of large scale telephony networks. Although copper has now largely been superseded in trunk or distribution networks by the use of optical fibre, many access networks, such as the local loops of public switched telephone networks, continue to employ copper. Globally, it is estimated that many tens of millions of tons of copper are deployed in such access networks and that this transmission medium may account for roughly one-half or more of the assets of the typical network operator.
As a transmission or delivery medium in modem communications networks, copper presents the challenge that it provides a theoretical maximum information rate of only approximately 35 kbps to 56 kbps across public switched telephone networks. Many technologies have emerged to extract higher bandwidth data transmissions from the existing copper based networks, due to a market demand for the delivery on such networks of higher bandwidth applications such as digital video and high-speed Internet access. For instance, a number of digital subscriber line or loop (DSL) architectures have been introduced in the last decade, each providing differing combinations of upstream data rates, downstream data rates and ranges of operation. Collectively, this family of digital subscriber line architectures is sometimes referred to as xDSL, and will be so referred to in this specification to denote all such digital subscriber line architecture.
The various xDSL architectures as introduced above cannot typically operate in ranges which exceed a few kilometers. For example, in high-speed digital subscriber loop (HDSL) technologies, data rates in the neighbourhood of 2 Mbps can be achieved by combining the capacity of two or three pairs. However, this is sustainable only over a distance of approximately 3 km. Using very high rate digital subscriber loop (VDSL) techniques, typical data rates of 23 Mbps in the downstream direction and 3 Mbps in the upstream direction can be attained, but only for distances in the neighbourhood of 1 kilometer at such rates.
Given the foregoing constraints, it has become necessary in the art to attempt to reduce the effective distance between a distribution backbone network and access terminals deployed within an access network, where the distribution backbone network employs a higher capacity transmission medium than that of the access network. In the illustrative case of a telephony access network consisting of a copper based local loop, the service provider central office is effectively brought in closer proximity to the end user subscriber by various means.
For instance, it is known in the art to employ scaled central office architectures, whereby a central office system is reduced in scale by reconfiguring an existing large scale switch to provide fewer user data ports. The scaled equipment is then deployed remotely from the central office and in closer proximity to the end user subscriber. This known solution suffers from a number of disadvantages. First, the scaled architecture employs the very same equipment infrastructure, such as control systems and power systems, as does the existing large scale equipment from which it is adapted. This tends to maintain the procurement cost and power requirements of the scaled equipment in a comparable range to that of the larger scale equipment. Second, the physical size of the scaled equipment is ordinarily the same as that of the large scale equipment, such that the known scaled architecture solutions typically do not offer an appreciable advantage as to physical size reduction. Thus, scaled architecture solutions as known in the art do not generally provide significant savings in respect of equipment procurement cost, operational power requirements or physical equipment size.
Another category of solutions in the prior art is that of repeatered architectures. Under such solutions, a subscriber line such as one provisioned for xDSL service is repeatered or carried via some other medium to thereafter be replicated at a remote location in closer proximity to the end user subscriber than is the central office equipment. This prior art category of solutions is disadvantageous in that it requires repeater equipment to be purchased, installed and maintained in addition to existing central office equipment.
Based on the foregoing prior art solutions, there is therefore a need for an alternate approach to the problem of reducing the effective distance between a distribution backbone network and access terminals deployed within an access network, where the distribution backbone network employs a higher capacity transmission medium than that of the access network.
Where the transmission medium of the local loop is typically copper and that of the distribution background network is a higher capacity transmission medium such as optical fibre, the exemplary network architecture and associated network components according to the present invention can advantageously be provisioned to result in an extension of the higher-capacity transmission medium of the distribution backbone network so that the latter is in closer physical proximity to the access terminals of the local loop. This may render the provisioning of higher bandwidth applications to network users more feasible than would otherwise be the case, while intending to alleviate some of the concerns and problems associated with the prior art solutions previously mentioned.